US Patent 7886709 Spring start for a vehicle engine

A spring assembly is mounted on a crankshaft for a vehicle. A selector mechanism for the spring assembly selectively connects the spring assembly to the crankshaft. The selector mechanism is engaged in a first position to connect the spring to the crankshaft when the engine is shut-off such that the crankshaft winds the spring as it rotates. The selector mechanism is then engaged in a second position such that the spring applies a rotational force to re-start the engine. A method for braking the engine includes engaging the crankshaft with the torsion spring and winding the torsion spring with rotation of the crankshaft until the tension within the torsion spring is greater than the force applied to the crankshaft.